The term "electroerosion" herein used is intended to include electrical discharge machining (EDM) and electrochemical machining (ECM) as well as electrochemical-discharge machining (ECMD) in which the principles of EDM and ECM are combined. The term "machining" is intended to refer to cutting, grinding and boring as well as to shaping with a tool electrode which may be tubular, cylindrical, elogated (wire, band or the like), of a disk-type or generally three-dimensional in shape depending on the particular mode of operation to be performed.
In an electroerosion process, a tool electrode is juxtaposed with a workpiece across a machining gap formed therebetween in the presence of a machining fluid and electrical energy is applied between the electrode and the workpiece to remove material from the latter by means of electrical discharge or electrochemical machining actions or both. As material removal proceeds, the tool electrode is displaced relative to the workpiece to maintain the gap spacing therebetween generally constant with the machining fluid being kept refreshed in the region of the machining gap.
The machining fluid, where it is desirably the aqueous type, has commonly or conveniently made use of municipal water which is utilized in a mixture with an electrolyte to form an ECM or ECDM machining fluid or deionized by an ion-exchange method up to a specific resistivity in the range between 10.sup.3 and 10.sup.4 ohm-cm to form an EDM machining fluid. With such machining fluid of the waterbase type, problems arise or the formation of etch pits on the machined surface of a workpiece; this is especially true when the latter is composed of copper, iron or aluminum.